The invention relates to an electro-magnetic vibration-damping mount for, more particularly, the engine in a vehicle.
An engine mount is described in U.S. Pat. No. 2,387,066. It is capable of mounting an internal-combustion engine in a motor vehicle where its purpose would be to prevent the transmission of troublesome vibrations between the engine and the chassis of the vehicle.
The vibrations introduced into such a vechicle engine mount are, principally, of two different origins.
One, with vibrations is in the frequency range above about 30 Hz, is produced by the engine itself. These vibrations manifest themselves as a throbbing in the vehicle and should be kept away from the vehicle chassis as much as possible to prevent this. In other words, they should be isolated, for example resiliently, without any forces being transmitted through the mount.
The other, with vibration frequencies up to about 12 Hz, is produced in the vehicle, in traveling over a rough road, for example. Under worst-case conditions, such vibrations can shake the engine damagingly with amplitudes of up to about 10 cm. In a passenger automobile, for example, such excursions cannot be tolerated and must be prevented. This can be done only by damping, for example, by braking the engine excursion with the relatively-immovable chassis. This involves a dynamic stiffening of the mount between the engine and chassis, in other words, a dynamic induration (hardening) of the engine mount which becomes effective with corresponding amplitudes of vibration excursion between the chassis and the engine.
This is what is involved in the design according to the patent cited. It results, however, in impairing the isolating action of the mount and, hence, in transmitting the throbbing vibrations from the engine to the chassis.
Optimum coordination of isolating action and damping action has not been readily possible heretofore, however, because both depend on the dimensioning of the structural elements and the like for interdependence. Modifications require differently-sized structural elements and thus entail great expense.